The Genetic Diagnosis and Counseling Core will perform genotyping on patients known to be afflicted with MEN-2 and related syndromes, their spouses, and all family members at greater than 25% risk. Both PCR and RFLP analysis will be employed to detect the presence of the disease locus. The interpretation of the results will be communicated to the genetic counseling staff who will then discuss these results with the patients. This core will also provide oligonucleotides to other participants in this program project. They will be synthesized in a timely fashion on an Applied Biosystems model 394 and distributed to the various laboratories.